This invention relates to paging systems which provide both individual and information services to subscribing paging receivers and, according to one aspect, to paging systems of the kind wherein a transmitter transmits page call address and data periodically in batches, each batch comprising a synchronization code word followed by a predetermined plurality of sequential frames; and wherein a battery saver paging receiver searches for both its individual service address and a first information service address in its corresponding assigned frame of each batch of a transmission period, and in response to reception of the first information service address, searches for a second information service address in a designated common frame of each batch of a transmission period. Individual and information service data messages are obtained from frames immediately subsequent the frame in which the respective individual and second information service addresses are found.
A typical system of the above kind is one employing the well-known POCSAG coding protocol in which each paging receiver of the system is assigned a frame of each batch to search for its individual service address or addresses. To alleviate frame crowding and render an efficient throughput, the frame assignments of the paging receivers of a paging system are uniformly distributed across the frames of each batch. It is also desirable to have these paging systems support information services of the kind where all users of paging receivers subscribing to the service can be automatically provided with information service data such as stock prices, sports results, weather reports, ... etc.
Accordingly, each paging receiver subscribing to an information service is typically programmed to respond to both an information service address and at least one individual service address. If the POCSAG method of frame assignment is used, i.e. for a given paging receiver, all addresses thereof are assigned to only one frame of a batch, all pagers must have both their individual and information service addresses in the same frame. Under these conditions, the paging system must transmit the information services data repeatedly for each frame of a batch in order to provide this data to all of the subscribing pagers. Since the information services data streams are generally long, retransmission for each frame of a batch results in a loss of valuable transmission air time which correlates directly to loss of profitability.
A solution to the aforedescribed drawback is to assign all paging receivers subscribing to both an information service and an individual service to a common frame of a batch, thereby requiring only one transmission of the information services data stream for each update and no retransmissions for other frames of the batch. This solution also results in a number of difficulties. First, when the number of information service paging receivers of a system is large, frame crowding of one frame of a batch occurs which creates system loading and throughput problems. Secondly, paging receivers currently in service may wish to add the information service capability which currently requires the inconvenience of changing the frame of their individual address to the common information service frame. This may also result in the pager being eliminated from a group call group which is confined to the original individual address frame. Alternatively, if the pager is forced to search for individual and group addresses in one frame and information service data in another frame of each batch, battery life of the paging receiver will be significantly degraded.
It is an object of the present invention to provide an improved paging system, transmitter, and paging receiver wherein the above disadvantages may be overcome or at least alleviated.